Goldtiger997 wrote:If we want to replicate this challenge with pseudo-still-lifes, all that needs to be synthesised in less than one glider per bit is this 14-bit pseudo-still-life: ...

Actually, my site is has a typo on it; the cis version of the above also takes 14 gliders. The synthesis shows that, even though it is listed as 12 on the stamp collection (unless there was a 12-glider synthesis somewhere that I forgot about. Does anyone remember one?)

On the plus side, pseudo-still-lifes are usually easier to synthesize than still-lifes, since most small pieces can be added for around 1 glider/bit or less, and the synthesis of the (now smaller) larger pieces has already been solved. On the minus side, apgsearch decomposes all pseudo-still-lifes into their component pieces, so soup searches will be of no use in finding cheap predecessors, unless one searches all soups that produce one of the component objects in the remote hope that it's formed as part of a pseudo-object.

On a related note, all pseudo-still-lifes up to 19 bits have been solved. All 20-bit ones can be synthesized except for the following 57 (the last 3 of which can be synthesized based on some of the others plus a snake-to-carrier converter);

Kayzan wrote:One of those unsynthesized pseudo still lifes was solved during the dart synthesis.

Thanks. I wasn't aware of that. I was in the hospital at that time, and their wifi login script was broken, so I didn't have internet access. I didn't look at the dart synthesis until much later, when it had a much simpler synthesis that no longer needed that pseudo-still-life.

EDIT: The initial pseudo-still-life (two blocks on two snakes) can be reduced by 4 from 17 to 13, by using the improved 5-glider up-snake-below-snake synthesis (I'm not sure where this came from), plus a new 4-glider block-hoisting converter. The final pseudo-still-life (#2) can be reduced by 6 more from 45 to 35 by using a pre-block rather than a house and a cheaper fleet. Luckily, the cleanup glider can be moved with no extra cost. (Sadly, these optimizations can only be done on one side, although there might be other ways to do one and/or the other on the other side as well).

The main reason I didn't complete the 15-bit still-lifes myself in the early 00s wasn't the difficulty of the task (I got about half of them done, and identified the problematic ones), but because of the sheer tedium of manually instantiating 1353 separate syntheses. There are 3286 16-bit still-lifes, more than any other collection of objects yet attempted for synthesis. I have syntheses for 352 of them (which would probably be good candidates for reduction), but that leaves an additional 2934 trivial syntheses that would have to be manually instantiated and vetted for cost. That is a task probably better suited to an automatic process.

mniemiec wrote:...That is a task probably better suited to an automatic process.

Maybe have some place where fully-exploded (i.e. gliders only, no intermediate steps) syntheses can be uploaded, then some web-based script could verify the glider count (simply read the total on-cells and divide by 5), run the synthesis to stabilization, then look up the resulting object and check whether it's a record?That looks like a lot but there are far messier options available.

I have been working on my glider synthesis analyser code that I have alluded to a couple of times on the forum. As of a few days ago I had computer-based verification that all 14-bit still lifes could be made in less than 14 gliders.

This evening I turned my code loose on Bob's still15.rar from a few posts back. Sadly there are some errors in the collection and I have not been able to fix them by looking at alternative sources (mniemiec's website or patterns posted on these forums).

Thanks guys. I should be able to finish off the 15 bit still lifes without too much more fiddling around. As a bit of a sneak preview here is a 3 glider tail adder that I found within the last week. It sets quite a few new records, for example I think 11.3 (a.k.a. down long boat with tail) goes from 7 gliders to 6:

chris_c wrote:Thanks guys. I should be able to finish off the 15 bit still lifes without too much more fiddling around. As a bit of a sneak preview here is a 3 glider tail adder that I found within the last week. It sets quite a few new records, for example I think 11.3 (a.k.a. down long boat with tail) goes from 7 gliders to 6: ...

Very nice! While it's a little bit bulkier than some of the previous ones, it's also more general than the previous 3-glider tail-adder (that only works on boats, barges, etc. facing away from the tail). This should improve a mind-bogglingly large number of syntheses. (Oh well, I had been planning on re-examining all 11000+ of them for recent improvement anyway...)